The manufacturing industry, and in particular the metal fabrication and stamping industries, commonly utilize automated systems that allow a workpiece to be conveyed or transferred between equally spaced workstations where particular operations are carried out. For example, many metal parts on automobiles and appliances are formed by means of a stamping procedure wherein a series of dies, that are situated on a number of aligned and equally spaced workstations within the bed of a transfer press, progressively form a workpiece upon each stroke of the press. Automated transfer systems are typically employed to grasp the workpiece, remove it from one set of dies and then transport the workpiece laterally through the press bed to the next adjacent workstation where it will be stamped a second time with a further set of dies upon the next stroke of the press.
A press transfer system utilized in conjunction with a typical multi-stage linear transfer press commonly includes at least one transversely oriented transfer rail situated adjacent to the press bed and aligned with the various workstations. Depending upon the particular application and the press layout, a single transfer rail may be positioned along one side of the press bed or, alternatively, a separate transfer rail may be located on each side of the bed of the press. Regardless, the primary function of the transfer rail is to provide a mechanism by which tools, generally referred to as grippers or fingers, may be supported adjacent to the workstations and are moved to allow a workpiece to be grasped and transported to the next workstation. Such grippers or fingers are often mounted either to the transfer rail or to a secondary tooling rail that is in some manner secured or attached to the transfer rail.
Movement of workpieces from workstation to workstation involves the movement of the transfer rail in what usually amounts to a relatively complex three dimensional manner. Described generally, this movement involves (i) moving the rail toward the workstation such that the grippers or fingers may grasp the workpiece (referred to as movement in the Y axis direction); (ii) lifting the rail upwardly to remove the workpiece from the dies of a particular workstation (referred to as movement in the Z axis direction); (iii) moving the rail laterally and parallel to the press bed to align the workpieces with the next adjacent workstation (referred to as movement in the X axis direction); (iv) lowering the rail to allow the grippers to place the workpieces onto the next adjacent set of dies (Z axis movement); (v) retracting the rail from the workstation (Y axis movement) to extract the grippers from the press bed so they are not damaged with the next stroke of the press; and, finally returning back to the starting position (X axis movement).
The primary reason for utilizing a press transfer system in fabrication and stamping operations is to maximize production efficiency through increasing the throughput of a production line. A press and its related equipment in a stamping or fabrication facility represents a significant capital investment for a manufacturer. In order to maximize the return on that investment there is a desire to maintain presses in continuous operation and to maximize the number of workpieces moving through the press over a given length of time. As a result others have devoted a considerable amount of effort into the design of transfer rails and the mechanical, electro-mechanical, hydraulic, and/or pneumatic systems that drive transfer rails in the complex three-dimensional manner described above. Still others have devoted much effort and expense in attempts to develop transfer rails that are light, rigid and sufficiently strong to facilitate rapid acceleration and deceleration as a means to increase press throughput.
While efforts in these regards have resulted in a marked improvement in the productivity when a press is in operation, little attention has been devoted to decreasing the down-time of a press when it becomes necessary to repair or replace the dies in the press bed, in circumstances where the press must be shut down for maintenance reasons, or where the fingers or grippers need to be changed or serviced. When access to the press bed is required for any of these reasons it has traditionally been necessary for the grippers or tools to be removed from the transfer rail (if a tool rail is used to hold the grippers the tool rail must be uncoupled from the transfer rail). At that point the transfer system may be moved to a “parked” position in which case the transfer rail would be moved horizontally outward from the press bed and lifted upwardly to allow unfettered and open access to the bed area of the press. Once the necessary work within the bed area has been completed the transfer system must be returned to is operational position and the grippers (or the tool rail) must be reinstalled before stamping operations can once again commence. It will be appreciated that such an operation can not only be time consuming, but can also require the services of a number of operators, adding significantly to the associated costs.